Acute graft-versus-host reactions (GVHRs) to a male-specific (H-Y) antigen have been investigated using a weight assay, a bone marrow assay and a focal periportal proliferation test. Severe acute GVHRs have been marrow assay a focal periportal proliferation test. Severe acute GVHRs have been induced by the injection of female DA rat cells into male (Dax Lewis) F1 hybrid rats. Besides semiallogeneic donor RT1 antigens, host H-Y antigen was concerned strongly with leading to systemic acute GVHRs. Even though there were clinical variations, the acute GVHRs to H-Y antigen were occurred in F1 males, especially by the immunization with DA female spleen cells. When F1 hosts were splenectomized, only mild to moderate acute GVHRs were recognived by the injection of either female or male donor cells. The donor cells obtained from Lewis females that were premmunized with one rat died of typical acute graft-versus-host disease (GVHD). But in the other 3, chromic graft rejection was suggested to add to the GVHRs. Hemolytic anemia and ballooning change of hepatocytes were developed at around 41-63 days after immunization. Acute GVHRs to H-Y antigen led to remarkable erythroid suppression on bone marrow and focal myeloid proliferation in liver
